System and method for communicating graphics image data over a communication network

ABSTRACT

A graphics adapter comprises a frame buffer operable to store graphics image data. The graphics adapter also comprises a network interface operable to receive at least a portion of the graphics image data, the network interface further operable to format the received graphics image data into a plurality of packets for transmission over a communication network.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to co-pending U.S. patent applicationSer. No. 10/004,191, entitled “SYSTEM AND METHOD FOR DISPLAYING AN IMAGEON A NETWORK ATTACHABLE DISPLAY DEVICE,” filed Oct. 31, 2001,co-assigned herewith.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of computersystems, and more particularly to a system and method for communicatinggraphics image data over a communication network.

BACKGROUND OF THE INVENTION

In existing computer systems, a user's input intended to modify theimage on the display is transmitted as a command with the associateddata from a CPU to a graphics adapter over an AGP (Accelerated GraphicsPort) and a PCI (Peripheral Component Interconnect) bus. A graphics chipon the graphics adapter renders the image based at least in part on thereceived command. Graphics image data associated with the rendered imageis stored in a frame buffer. The image information is typically storedin the frame buffer in a digital format. The digital data stored in theframe buffer controls the color and intensity of every pixel on thedisplay. The graphics adapter may include a RAMDAC (Random Access MemoryDigital-to-Analog Converter) to convert graphics image data stored inthe frame buffer from digital to analog form for display on an analogdisplay.

The RAMDAC may be part of or separate from a display refresh unit.Depending on the refresh rate of the display, the display refresh unitfrequently reads the contents of the frame buffer. If desired, theRAMDAC may convert the information into analog form and send it to themonitor. Thus, for a 1280×1024 pixel display using 24 bits per pixel,approximately 4 MB of data has to be read from the frame buffer for eachrefresh of the display. If the refresh rate of the display is 70 timesper second, then approximately 280 MB of data is transmitted from thegraphics adapter every second.

Two resources in the graphics adapter compete for the same framebuffer—the rendering unit and the display refresh unit. The renderingunit and the display refresh unit may be part of the same graphics chip.Because of the frequent and constant access of the frame buffer by thedisplay refresh unit required to transfer large amounts of data, therendering performance of the graphics adapter is adversely affected.

Furthermore, it is often desirable to display graphics information thatis generated by a computer on a remote display monitor. Sometimes it isdesirable to provide this type of remote graphics display across acommunication network. One approach to providing graphics image data toa remote display involves reading data from the frame buffer back intothe memory of the computer system, compressing the data, assembling thedata into IP (Internet Protocol) packets, and then sending the packetsto the destination computer over the communication network.

The destination computer receives the compressed image via a networkinterface card and stores it in system memory. The compressed image istransmitted to a PCI card where it is decompressed. The decompressedimage is transmitted back to the system memory. The decompressed imageis then transmitted to a graphics adapter on the destination computervia an AGP or a PCI bus. The graphics adapter transmits video signalsover a video cable to the display, typically a CRT (Cathode Ray Tube),or LCD (Liquid Crystal Display) to display the graphics image. It may beseen from the foregoing that there is considerable data movement on thedestination computer which increases the latency.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, a graphicsadapter comprises a frame buffer operable to store graphics image data.The graphics adapter also comprises a network interface operable toreceive at least a portion of the graphics image data, the networkinterface further operable to format the received graphics image datainto a plurality of packets for transmission over a communicationnetwork.

In accordance with another embodiment of the present invention, a methodfor transmitting graphics image data over a communication network isdisclosed. The method comprises logically dividing a frame buffer of agraphics adapter into a plurality of segments, each of the plurality ofsegments storing graphics image data corresponding to a destinationdevice of a plurality of destination devices; selecting a segment of theplurality of segments corresponding to a destination device of theplurality of destination devices; and formatting at least a portion ofthe graphics image data stored in the selected segment into a pluralityof packets for transmission by a network interface of the graphicsadapter to the destination device over the communication network.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, the objectsand advantages thereof, reference is now made to the followingdescriptions taken in connection with the accompanying drawings inwhich:

FIG. 1 is a block diagram of an exemplary system in which a graphicsadapter of the present invention may be used;

FIGS. 2A-2B are logical block diagrams of a graphics adapter inaccordance with different embodiments of the present invention;

FIG. 3 is a flowchart describing the operation of a graphics adapter inaccordance with an embodiment of the present invention.

FIG. 4 is a flowchart describing the operation of a graphics adapter inaccordance with another embodiment of the present invention;

FIG. 5 is a flowchart describing the operation of a graphics adapter inaccordance with a further embodiment of the present invention;

FIG. 6 is a flowchart describing the operation of a graphics adapter inaccordance with yet another embodiment of the present invention;

FIGS. 7A-7B are logical block diagrams of a network attachable displaydevice in accordance with different embodiments of the presentinvention;

FIG. 8 is a flowchart describing the operation of a network attachabledisplay device in accordance with an embodiment of the presentinvention; and

FIG. 9 is a flowchart describing the operation of a network attachabledisplay device in accordance with another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the present invention and its advantages arebest understood by referring to FIGS. 1 through 9 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

There is a desire for an improved system and method for communicatinggraphics image data over a communication network, such as a computernetwork. Accordingly, a graphics adapter comprising a compression unitand a network interface, capable of communicating with a destinationdevice, such as a remote computer, over a communication network, such asa computer network, is disclosed. The graphics adapter also includes amemory unit, such as a frame buffer. In addition to or in place of oneor more video output ports, such as analog video ports, Digital VisualInterface (DVI) video ports, and the like, that are included in existinggraphics adapters, the graphics adapter in accordance with the presentinvention may be provided with a network interface port, for example anEthernet port, an Infiniband port, a fiber port, a wireless networktransceiver, and the like. The network interface port may be used fortransmitting the contents of the frame buffer in either compressed oruncompressed form via the computer network to one or more remotecomputers.

FIG. 1 is a block diagram of an exemplary system 10 in which thegraphics adapter of the present invention may be used. System 10preferably comprises at least one source device 12, such as at least oneprocessor-based system, for example computers, and at least onedestination device 14. Destination device 14 may comprise, for example adisplay device capable of being directly coupled to a communicationnetwork, a display associated with a computer, and the like. One or moresource devices 12 may communicate with each other over a communicationnetwork (not shown), such as a local area network. Source device 12preferably communicates with destination device 14 over a communicationnetwork 16. Communication network 16 may comprise an intranet, anextranet and/or the Internet.

Source device 12 may comprise a graphics adapter 20. However, inalternative embodiments, graphics adapter 20 may not be part of sourcedevice 12. In such an embodiment, graphics adapter 20 may be coupleddirectly to communication network 16.

FIG. 2A is a logical block diagram of a graphics adapter 20 inaccordance with an embodiment of the present invention. Graphics adapter20 comprises a network interface chip 38 coupled to a memory unit 24. Agraphics chipset 22 is also preferably coupled to memory unit 24.Network interface chip 38 preferably comprises a compression unit 26 anda network interface 28. If desired, graphics adapter 20 may alsocomprise at least one video transmitter, for example an analogtransmitter 30 and a digital transmitter 32, coupled to memory unit 24.Preferably, analog transmitter 30 and digital transmitter 32 are alsocoupled to each other. If desired, network interface chip 38 may becoupled to graphics chipset 22.

Graphics chipset 22 is a conventional graphics chipset which renders theimage to be displayed on destination device 14. The image may berendered based at least in part on instructions received from a memoryunit of source device 12 or instructions received from destinationdevice 14. Instructions from source device 12 are preferably receivedvia a graphics port 34. Graphics port 34 may be a Peripheral ComponentInterconnect (PCI) port, an Accelerated Graphics Port (AGP), anInfiniband Port, a fiber port and the like. In an alternativeembodiment, instructions may be received via a network interface port36. In such an embodiment, graphics adapter 20 may not include graphicsport 34. Rendering of an image typically comprises translatinghigh-level instruction to bitmap images which are a matrix of pixels.The process of rendering is known in the art and as such will not bedescribed in detail herein.

Memory unit 24 preferably comprises a frame buffer 50. Frame buffer 50is used to store information about the rendered image. Frame buffer 50may store information, such as color, transparency values, depth and/orthe like, for each pixel in the rendered image.

Compression unit 26 of network interface chip 38 preferably compressesthe data stored in frame buffer 50. Compression unit 26 includescompression logic optimized for use with graphics image data stored inframe buffer 50. However, the invention is not so limited and any kindof compression logic may be used by compression unit 26. Compressionunit 26 may be implemented using general-purpose hardware components,such as a digital signal processor or microprocessor, and appropriatesoftware for controlling the operation of the hardware components. Ifdesired, compression unit 26 may be implemented using dedicatedhardware, an Application Specific Integrated Circuit (ASIC) or a FieldProgrammable Gate Array (FPGA) that is specially designed for carryingout the compression.

Network interface 28 formats the graphics image data for transmissionover a network, such as communication network 16. A network interfaceport 36, for example an Ethernet port, an Infiniband port, a fiber port,a wireless network transceiver, and the like, is preferably coupled tonetwork interface chip 38. Network interface 28 converts the graphicsimage data into packets to be transmitted to destination device 14 vianetwork interface port 36 over communication network 16. The graphicsimage data may be obtained by network interface 28 either fromcompression unit 26 or from frame buffer 50. For example, in oneembodiment, graphics image data from frame buffer 50 may be compressedby compression unit 26 and provided to network interface 28. In anotherembodiment, after compressing the graphics image data, compression unit26 may provide the data back to frame buffer 50 and network interface 28may read the compressed graphics image data directly from frame buffer50. In yet another embodiment, for example when compression of graphicsimage data is not desired, network interface 28 may read graphics imagedata directly from frame buffer 50.

Analog transmitter 30 comprises a conventional RAMDAC and may be used toconvert graphics image data stored in memory unit 24 from digital formatinto an analog format to be transmitted to an analog device, such as ananalog monitor which may be coupled to source device 12, via analogvideo port 40. Digital transmitter 32 comprises a conventional DigitalVisual Interface (DVI) transmitter and may be used to transmit graphicsimage data in digital format from memory unit 24 to a digital device,such as a digital monitor which may be coupled to source device 12, viadigital video port 42.

FIG. 2B is a logical block diagram of graphics adapter 20 in accordancewith another embodiment of the present invention. Graphics adapter 20 asshown in FIG. 2B comprises a network attachable graphics chip 52 coupledto memory unit 24. Network attachable graphics chip 52 comprises agraphics unit 44, compression unit 26 and network interface 28. Ifdesired, graphics adapter 20 may also comprise at least one videotransmitter, for example analog transmitter 30 and digital transmitter32, coupled to memory unit 24. Preferably, analog transmitter 30 anddigital transmitter 32 are also coupled to each other. In graphicsadapter 20 of FIG. 2B, network interface port 36 is preferably coupledto network attachable graphics chip 52. Graphics unit 44 performssubstantially the same function as graphics chipset 22 of FIG. 2A.

One of the advantages of graphics adapter 20 of FIG. 2B over theembodiment of FIG. 2A is that the manufacturing cost of the graphicsadapter can be reduced as only one chip, network attachable graphicschip 52, is used in the embodiment of FIG. 2B.

In an alternative embodiment, graphics adapter 20 does not includeanalog transmitter 30 or digital transmitter 32. In yet anotherembodiment, graphics adapter 20 does not include analog video port 40and digital video port 42; graphics image data is transmitted to sourcedevice 12 via network interface port 36.

In yet another embodiment of the present invention, graphics adapter 20does not include graphics port 34 for receiving graphics commands.Instead graphics adapter 20 receives graphics commands overcommunication network 16 via network interface port 36. The graphicscommand may be received from source device 12 or from destination device14.

FIG. 3 is a flowchart 90 describing the operation of graphics adapter 20in accordance with an embodiment of the present invention. In step 92,the graphics adapter waits for either the lapse of a predeterminedperiod of time or the receipt of an update request. The predeterminedperiod of time may be dependent upon the refresh rate of a displayassociated with destination device 14. Destination device 14 itself maybe the display. The update request may be received by graphics adapter20 from source device 12 via graphics port 34. The request may also bereceived by the graphics adapter from destination device 14 via networkinterface port 36 over communication network 16.

Upon the occurrence of one of the above events, a determination is madein step 94 as to whether the graphics image data in frame buffer 50 hasbeen changed since the last update. If the graphics image data in framebuffer 50 has not been changed, then the process starting at step 92 isrepeated. The step of determining whether the graphics image data inframe buffer 50 has been changed is optional and has been shown in FIG.3 by dashed lines.

In the preferred embodiment of step 94, a flag is read to determinewhether the graphics image data in frame buffer 50 associated with thedestination device has been updated since the last transmission. Theflag may have been previously set by graphics chipset 22 during a writeto frame buffer 50. For example, when information for each pixel iswritten into frame buffer 50, the pixel value could be compared with apreviously stored value, and the flag is set if there has been a change.If desired, the particular region of frame buffer 50 associated with thedestination device that has changed may also be tracked, for example bytracking the minimum and maximum values in the x and y coordinates forthe region that has changed.

In step 98, graphics image data from frame buffer 50 is read bycompression unit 26. If desired, color coalescing may be performed inthis step. A Display Refresh Unit (DRU) may perform the task of colorcoalescing. The DRU may be part of the network interface chip or may becoupled to the network interface chip. Color coalescing is the processof merging images of multiple display surfaces, such as a primarydisplay surface and one or more overlay planes into a single image. Oneor more color look-up tables containing colors for the pixels may bestored in registers (not shown) on graphics chipset 22. A windowidentifier may be used to determine the color look-up table to be used.Based on the value for the pixels stored in frame buffer 50, the colorsfor the pixels are obtained from the determined color look-up table.

In step 100, a determination is made as to whether compression isenabled. A compression bit within a register (not shown) on graphicschipset 22 may be read to determine if compression is enabled or not. Ifcompression is enabled, then in step 102, graphics image data read fromframe buffer 50 is compressed preferably by compression unit 26.Preferably, a compression algorithm optimized for compressing graphicsimage data read from frame buffer 50 is used. However, any of a varietyof compression algorithms may be used by compression unit 26 to compressthe data read from frame buffer 50. After compression, compression unit26 may write the compressed data back to frame buffer 50. Compression ofgraphics image data prior to transmission over communication network 16significantly reduces the amount of data that is transmitted overcommunication network 16.

If, in step 100, it is determined that compression is not enabled, thenexecution proceeds directly to step 104. In step 104, graphics imagedata is formatted for communication over communication network 16,preferably by network interface 28. Network interface 28 may readgraphics image data from frame buffer 50 or may receive graphics imagedata directly from compression unit 26. In a preferred embodiment,graphics image data, whether in compressed form or in uncompressed form,is formatted into a plurality of packets suitable for transmission overcommunication network 16 using a communication protocol, such asInternet Protocol (IP). The formatted data packets include, among otherthings, identification information of destination device 14 to which thegraphics image data is to be transmitted. Identification information mayinclude for example an IP address of destination device 14.Identification information about destination device 14 may be receivedby graphics adapter 20 either from source device 12 or from destinationdevice 14 itself.

In step 106, the formatted graphics image data is transmitted overcommunication network 16 to destination device 14, preferably as one ormore Internet Protocol (IP) packets. The packets include a portion ofthe graphics image data (payload) and identification information aboutdestination device 14. If desired, the same graphics image data may betransmitted to more than one destination device 14. This may beaccomplished, for example, by creating data packets with the samepayload but different identification information corresponding to thedifferent destination devices. If desired, the formatted graphics imagedata may be transmitted via graphics port 34 to source device 12.Transmitting the graphics image data to source device 12 allows thesource device to perform further processing of the graphics image dataas desired. By transmitting packets with the same payload to more thanone destination device, the same data may be presented to users ofmultiple destination devices, thereby enabling sharing of graphics imagedata by these multiple users. If desired, different graphics image datamay be transmitted from graphics adapter 20 to the different users asdescribed herein with reference to FIG. 6.

FIG. 4 is a flowchart 110 describing the operation of a graphics adapterin accordance with another embodiment of the present invention. In step112, the graphics adapter receives a request for an updated image fromdestination device 14. The request is received preferably overcommunication network 16 via network interface port 36. Informationidentifying destination device 14 may also be received from destinationdevice 14.

In step 116, graphics image data is stored in frame buffer 50. In step118, graphics image data from frame buffer 50 is read preferably bycompression unit 26. If desired, color coalescing may be performed inthis step. In step 120, a determination is made as to whethercompression is enabled. If compression is enabled, then in step 122,graphics image data read from frame buffer 50 is compressed preferablyby compression unit 26.

If, in step 120, it is determined that compression is not enabled, thenexecution proceeds directly to step 124. In step 124, the graphics imagedata is formatted for communication over communication network 16,preferably by network interface 28. Network interface 28 may readgraphics image data from frame buffer 50 or may receive graphics imagedata directly from compression unit 26. In a preferred embodiment,graphics image data, whether in compressed form or in uncompressed form,is formatted into a plurality of packets suitable for transmission overcommunication network 16 using a communication protocol, such asInternet Protocol (IP). The formatted data packets include, among otherthings, identification information of destination device 14 to which thegraphics image data is to be transmitted. Identification information mayinclude for example an IP address of destination device 14. In step 126,the formatted graphics image data is transmitted over communicationnetwork 16 to destination device 14, preferably as one or more IPpackets.

FIG. 5 is a flowchart 130 describing the operation of a graphics adapterin accordance with a further embodiment of the present invention. In themethod of flowchart 130 only the portions of the frame buffer that havechanged since the last update are transmitted to destination device 14.Graphics image data for a display may be effectively partitioned into aplurality of blocks, for example 16,384 blocks. As mapped to a display,these blocks may comprise an array of 128 blocks by 128 blocks. In adisplay having a resolution of 1,280 pixels by 1,024 pixels, each blockhas a corresponding resolution of 10 pixels by 8 pixels. However, thepresent invention is not so limited and a number of different blocksizes may be chosen based upon system resources, the nature of thegraphics image data to be transmitted, and a number of other factors.

Preferably, frame buffer 50 of graphics adapter of FIGS. 2A-2B storesinformation about both a new image and a previous image so thatcomparisons between the two images may be made. In step 132, thegraphics adapter waits for either the lapse of a predetermined period oftime or the receipt of an update request. The predetermined period oftime may be dependent upon the refresh rate of a display associated withdestination device 14. The request for an update may be received fromsource device 12 with which the graphics adapter is associated viagraphics port 34. The request may be received by the graphics adapterfrom destination device 14 via network interface port 36 overcommunication network 16.

In step 134, portions or blocks of the graphics image data stored in theframe buffer corresponding to the new image are compared tocorresponding portions or blocks of the graphics image data stored inthe frame buffer corresponding to the previous image. In step 136, adetermination is made as to whether any portions have changed since thelast update. If the graphics image data has not been changed then theprocess starting at step 132 is repeated.

In step 138, a determination is made as to whether compression isenabled. If compression is enabled, then in step 140, graphics imagedata for portions or blocks of the new image that are determined to bedifferent from the corresponding portions or blocks of the previousimage are compressed. In an alternative embodiment, only those blocksthat have changed since the last update and are within a “region ofinterest” specified by destination device 14 are compressed. This may bedesirable, for example, when destination device 14 only desires toupdate specific portions of its display, for example a specific windowof a plurality of windows.

If, at step 138, it is determined that compression is not enabled, thenexecution proceeds directly to step 142. In step 142, graphics imagedata for blocks that have changed is formatted for communication overcommunication network 16, preferably by network interface 28. In apreferred embodiment, graphics image data in any block with any changeat all from the previously stored block may be formatted. If desired,some threshold for change may be set. The graphics adapter may beconfigured to evaluate the degree or amount of change and format thegraphics image data only if it has changed by some predetermined amount.

Network interface 28 may read graphics image data from frame buffer 50or may receive graphics image data directly from compression unit 26. Ina preferred embodiment, graphics image data associated with any blocksthat have changed, whether in compressed form or in uncompressed form,is formatted into a plurality of packets suitable for transmission overcommunication network 16 using a communication protocol, such asInternet Protocol (IP). A packet may include one or more blocks ofgraphics image data. The formatted data packets include, among otherthings, identification information of destination device 14 to which thegraphics image data is to be transmitted. Identification information mayinclude for example an IP address of destination device 14.Identification information about destination device 14 may be providedto the graphics adapter either from source device 12 or from destinationdevice 14 itself.

In step 144, block identifiers (IDs) are added to the packets of data tobe transmitted. The block ID information is preferably used bydestination device 14 for updating a display associated with it. A blockID identifies the particular block for which graphics image data isbeing transmitted. A block ID may be a block number. If desired, theminimum and maximum values in the x and y coordinates (X_(min), X_(max),Y_(min), Y_(max)) for the block may be used as the block ID. The fourcorners of the block that is identified by the minimum and maximumvalues in the x and y coordinates are given by (X_(min), Y_(min)),(X_(max), Y_(min)), (X_(max), Y_(max)) and (X_(min), Y_(max)).

In step 146, formatted graphics image data is transmitted overcommunication network 16 to destination device 14, preferably as one ormore IP packets. If, desired, formatted graphics image data may betransmitted over graphics port 34 to source device 12. The same graphicsimage data may be transmitted to one or more destination devices 14.This may be accomplished, for example, by creating data packets with thesame payload but including identification information, such as IPaddresses, for different destination devices in the data packets.

In step 148, one or more blocks of frame buffer 50 corresponding to theprevious image are updated. Preferably, only the blocks of the framebuffer associated with the previous image that have changed areoverwritten by graphics image data for the corresponding blocks of thenew image. If desired, the entire portion of the frame buffer associatedwith the previous image may be overwritten by graphics image data fromthe frame buffer associated with the new image.

It may be desirable to periodically transmit an entire frame bufferassociated with a display to avoid problems that may occur due topackets lost in transmission or otherwise. If desired, destinationdevice 14 may be configured to transmit acknowledgements back to thegraphics adapter to better ensure proper synchronization between thegraphics adapter and destination device 14.

FIG. 6 is a flowchart 150 describing the operation of a graphics adapterin accordance with yet another embodiment of the present invention. Themethod as described herein with reference to FIG. 6 may be used toprovide support for multiple destination devices by the same graphicsadapter. The graphics adapter of the present invention may be used torender graphics for multiple destination devices, such as multiplecomputers, coupled to communication network 16. Graphics image data maybe transmitted from the graphics adapter to the destination devices vianetwork interface port 36 over communication network 16 without the needfor separate ports for the different destination devices. Thus, thenumber of destination devices that may be supported is not limited bythe number of physical ports associated with the graphics adapter.

In step 152, the graphics adapter waits for either the lapse of apredetermined period of time or the receipt of an update request. Thepredetermined period of time may be dependent upon the refresh rate of adisplay associated with a destination device. The request for an updatemay be received by the graphics adapter from source device 12 with whichthe graphics adapter is associated via graphics port 34. The request maybe received by the graphics adapter from destination device 14 vianetwork interface port 36 over communication network 16.

Upon the occurrence of one of the above events, in step 154, the portionof frame buffer 50 corresponding to destination device 14 to whichgraphics image data is to be transmitted is determined. In the preferredembodiment, a destination device table may be looked up to determine theportion of the frame buffer 50 corresponding to the destination device.The destination device table preferably includes information about oneor more destination devices, such as identification information of thedestination device, the region of frame buffer 50 assigned to thedestination device, information indicating whether graphics image datacorresponding to the destination device has changed, and/or the like.

In step 156 a determination is made as to whether the graphics imagedata corresponding to the destination device in frame buffer 50 has beenchanged since the last update. If the graphics image data in framebuffer 50 has not been changed, then the process starting at step 152 isrepeated. The step of determining whether the graphics image data inframe buffer 50 has been changed is optional and has been shown in FIG.6 by dashed lines.

In step 158, a determination is made as to whether compression isenabled. If compression is enabled, then in step 160, graphics imagedata stored in the portion of frame buffer 50 associated with theparticular destination device is compressed preferably by compressionunit 26.

If, in step 158, it is determined that compression is not enabled, thenexecution proceeds directly to step 162. In step 162, the graphics imagedata associated with the particular destination device 14 is formattedfor communication over communication network 16, preferably by networkinterface 28. Network interface 28 may read graphics image data fromframe buffer 50 or may receive graphics image data directly fromcompression unit 26. In a preferred embodiment, graphics image data,whether in compressed form or in uncompressed form, is formatted into aplurality of packets suitable for transmission over communicationnetwork 16 using a communication protocol, such as Internet Protocol.The formatted data packets include, among other things, identificationinformation of destination device 14 to which the graphics image data isto be transmitted. Identification information may include for example anIP address of the particular destination device 14. Identificationinformation about destination device 14 may be received by the graphicsadapter either from source device 12 or from destination device 14itself.

In step 164, the formatted graphics image data is transmitted overcommunication network 16 to destination device 14, preferably as one ormore IP packets.

A technical advantage of an exemplary embodiment of the graphics adapterof the present invention is that graphics image data does not have to betransferred back into the memory of the source computer in order to betransferred to a destination device. Because the graphics adapter may bedirectly connected to a communication network, graphics image data fromthe graphics adapter may be directly transmitted over the communicationnetwork to the destination device. Another technical advantage of anexemplary embodiment of the graphics adapter of the present invention isthat graphics image data of the frame buffer is transmitted to thedestination device only if the contents of the frame buffer havechanged. Moreover, if desired, graphics image data for only particularregions of interest, for example, the blocks of the frame buffer thathave changed, may be transmitted, thereby eliminating the need totransmit the contents of the entire frame buffer with every update.

Moreover, the graphics image data may be tagged or addressed and sent tomore than one destination device. Thus, multiple destination devices maybe simultaneously supported by the same graphics adapter without beinglimited by the number of physical ports associated with the graphicsadapter. The multiple destination devices may be provided with the sameimage data thereby allowing multiple users to collaborate on the sameproject. If desired, different portions of the frame buffer may beallocated to different destination devices and the multiple destinationdevices provided with different data.

FIG. 7A is a logical block diagram of a network attachable displaydevice 14 in accordance with an embodiment of the present invention.Network attachable display device 14 comprises a display networkinterface 172 coupled to a display memory unit 174, a displaydecompression unit 176 and a display refresh unit 178. Display memoryunit 174 is also coupled to display decompression unit 176 and displayrefresh unit 178. Display decompression unit 176 is also coupled todisplay refresh unit 178 and display refresh unit 178 is also coupled toa display unit 180.

Network attachable display device 14 of the preferred embodiment iscapable of being coupled to a communication network, such ascommunication network 16. Thus, network attachable display device 14 maycommunicate with other devices coupled to communication network 16 andmay receive and/or transmit commands and/or data to and from suchdevices over communication network 16 via network interface port 182.

Display network interface 172 is operable to receive data, such asgraphics image data, from a source device, such as source device 12,graphics adapter 20, a graphics appliance, and/or the like, over acommunication network, such as communication network 16, via a displaynetwork interface port 182, for example an Ethernet port, an Infinibandport, a fiber port, a wireless network transceiver, and the like. Thegraphics image data is preferably received in a packetized format.

Display memory unit 174 preferably comprises a display frame buffer 170.Display frame buffer 170 is used to store graphics image data that is tobe displayed on display unit 180. The graphics image data may be storedin display frame buffer 170 in either compressed or decompressed form.Display frame buffer 170 may store information, such as color for eachpixel to be displayed on display unit 180.

Display decompression unit 176 preferably decompresses the data receivedby display network interface 172. Display decompression unit 176includes decompression logic optimized for use with graphics image data.However, the invention is not so limited and any kind of decompressionlogic may be used by display decompression unit 176. Displaydecompression unit 176 may be implemented using general-purpose hardwarecomponents, such as a digital signal processor or microprocessor, andappropriate software for controlling the operation of the hardwarecomponents. If desired, display decompression unit 176 may beimplemented using dedicated hardware, an ASIC or a FPGA that isspecially designed for carrying out the decompression. In the embodimentshown in FIG. 7A, display decompression unit 176 is also coupled todisplay network interface 172 and display refresh unit 178.

Display refresh unit 178 is a conventional display refresh unittypically used in graphics adapters. In the embodiment shown in FIG. 7A,display refresh unit 178 is coupled to display unit 180. Display unit180 preferably comprises a CRT (Cathode Ray Tube). In alternativeembodiments, display unit 180 may comprise a Liquid Crystal Display(LCD), a Thin Film Transistor (TFT), a Light Emitting Diode (LED),organic polymers and/or the like now known or later developed. Dependingon the display refresh rate of display unit 180, display refresh unit178 reads the graphics image data from display frame buffer 170frequently and refreshes display unit 180 at the refresh rate of displayunit 180.

Display unit 180 is preferably logically divided into horizontalsegments. Preferably display unit 180 is refreshed starting from the topleft corner of the desired portion of display unit 180 and moving to theright. Once a horizontal segment of display unit 180 is refreshed, thenext horizontal segment is refreshed starting from the left and movingto the right until the desired portion of display unit 180 is refreshed.This process is repeated frequently depending on the display refreshrate of display unit 180.

FIG. 7B is a logical block diagram of a network attachable displaydevice 14 in accordance with another embodiment of the presentinvention. Network attachable display device 14 as shown in FIG. 7Bcomprises a network attachable display controller 186 coupled to displaymemory unit 174 and display unit 180. Network attachable displaycontroller 186 comprises display network interface 172, displaydecompression unit 176 and display refresh unit 178. In networkattachable display device 14 of FIG. 7B, display network interface port182 is coupled to network attachable display controller 186.

One of the advantages of network attachable display device 14 of FIG. 7Bover network attachable display device 14 of FIG. 7A is that themanufacturing cost of the network attachable display device can bereduced as a single chip, network attachable display controller 186,includes the functionality of display network interface 172, displaydecompression unit 176 and display refresh unit 178.

FIG. 8 is a flowchart 190 of a method of operation of a networkattachable display device in accordance with an embodiment of thepresent invention. In step 192, graphics image data is received from asource device, such as a computer, a graphics device, a server, anInternet appliance and/or the like, for example source device 12 orgraphics adapter 20, over a communication network, such as communicationnetwork 16, via display network interface port 182. The data is receivedpreferably as a plurality of packets. Display network interface 172assembles the received data in a format suitable for storage in displayframe buffer 170. For example, if the packets of data includeinformation indicating the portions of display unit 180 with which thedata included in the packets are associated, then display networkinterface 172 stores the data in the appropriate portions of displayframe buffer 170.

In step 194, the assembled graphics image data is stored in displayframe buffer 170. In step 196, a determination is made as to whether thegraphics image data stored in display frame buffer 170 is in compressedform. If the stored graphics image data is in compressed form, then instep 198 the stored graphics image data is decompressed, preferably bydisplay decompression unit 176. In step 200, decompressed data is storedin display frame buffer 170.

If, in step 196, it is determined that the graphics image data stored indisplay frame buffer 170 is not in compressed form, then executionproceeds directly to step 202. In step 202, graphics image data is readfrom display frame buffer 170. Preferably, display refresh unit 178reads the data from display frame buffer 170 and refreshes display unit180 at the display refresh rate of display unit 180.

FIG. 9 is a flowchart 206 of a method of operation of a networkattachable display device in accordance with another embodiment of thepresent invention. In step 208, graphics image data is received from asource device, such as a computer, a graphics device, a server, anInternet appliance and/or the like, for example source device 12 orgraphics adapter 20, over a communication network, such as communicationnetwork 16 via display network interface port 182. The data is receivedpreferably as a plurality of packets.

In step 210, a determination is made as to whether the graphics imagedata stored in display frame buffer 170 is in compressed form. If thegraphics image data is in compressed form, then in step 212, displaynetwork interface 172 provides the graphics image data to displaydecompression unit 176 and the graphics image data is decompressed,preferably by display decompression unit 176, preferably “on the fly”.For this purpose graphics image data received by display networkinterface 172 is transferred to display decompression unit 176 anddisplay decompression unit 176 decompresses the graphics image data “onthe fly”.

If, in step 210, it is determined that the graphics image data stored indisplay frame buffer 170 is not in compressed form, then executionproceeds directly to step 214. In step 214, decompressed data is storedin display frame buffer 170.

In step 216, graphics image data is read from display frame buffer 170.Preferably, display refresh unit 178 reads the data from display framebuffer 170 and refreshes display unit 180 at the display refresh rate ofdisplay unit 180.

Preferably, display frame buffer 170 stores graphics image datacorresponding to both a new image and a previous image. Graphics imagedata corresponding to the previous image is preferably graphics imagedata for the image currently displayed on display unit 180. Graphicsimage data corresponding to the new image is preferably graphics imagedata for the image to be displayed on display unit 180. Once displaydecompression unit 176 or display network interface 172 has storedgraphics image data corresponding to the new image in display framebuffer 170, display refresh unit 178 may read graphics image data fromthe portion of display frame buffer 170 corresponding to the new image.After a new image has been displayed on display unit 180, the graphicsimage data corresponding to the previous image may be overwritten by thegraphics image data for the new image. Thereafter, display refresh unit178 may read graphics image data from the portion of display framebuffer 170 corresponding to the previous image and refresh display unit180 at the display refresh rate.

The use of display frame buffer 170 to store graphics image data relatedto both the new image and the previous image prevents “tearing” of thedisplayed image which may otherwise result if the display refresh unit178 is refreshing the display unit 180 at a rate which is faster thanthe rate at which graphics image data related to the new image is beingwritten to display frame buffer 170. The use of display frame buffer 170to store graphics image data related to both the new image and theprevious image may be avoided if graphics image data corresponding tothe new image is stored in display frame buffer 170 at least as fast asthe rate at which display unit 180 is refreshed.

A technical advantage of an exemplary embodiment of the networkattachable display device of the present invention is that graphicsimage data does not have to be transferred into the memory of a computerin order to be displayed on the network attachable display device.Because the network attachable display device may be directly connectedto a communication network, graphics image data may be directly receivedover the communication network by the network attachable display deviceitself.

1. A method for transmitting graphics image data over a communicationnetwork, comprising: comparing graphics image data of a new image for adestination device with graphics image data of a previous image for saiddestination device stored in a frame buffer of a graphics adapter remotefrom said destination device, said graphics adapter rendering saidgraphics image data for said new image and said previous image;selecting blocks of graphics image data of said new image that aredifferent from corresponding blocks of graphics image data of saidprevious image in a region of interest of said previous image specifiedby said destination device, wherein said region of interest is a portionof said previous image, and formatting, by said graphics adapter, saidselected blocks of graphics image data of said new image into aplurality of packets for transmission by a network interface of saidgraphics adapter over said communication network.
 2. The method of claim1, further comprising transmitting said plurality of packets to saiddestination device over said communication network.
 3. The method ofclaim 1, further comprising compressing said selected blocks of graphicsimage data prior to formatting said selected blocks of graphics imagedata.
 4. The method of claim 1, further comprising adding identificationinformation identifying said selected blocks to said plurality ofpackets.
 5. The method of claim 4, wherein said identificationinformation comprises block numbers for said selected blocks.
 6. Themethod of claim 4, wherein said identification information comprisescoordinate information for a plurality of corners of said selectedblocks.
 7. The method of claim 2, further comprising waiting for arequest for graphics image data from said destination device.
 8. Agraphics processing system, comprising: a graphics adapter configured tocompare graphics image data of a new image for a destination device withgraphics image data of a previous image for said destination devicestored in a frame buffer of said graphics adapter, said graphics adapterlocated remote from said destination device, said graphics adapterconfigured to render said graphics image data for said new image andsaid previous image, the graphics adapter configured to select blocks ofgraphics image data of said new image that are different fromcorresponding blocks of graphics image data of said previous image in aregion of interest of said previous image specified by the destinationdevice, wherein said region of interest is a portion of said previousimage, and format said selected blocks of graphics image data of saidnew image into a plurality of packets for transmission by a networkinterface of said graphics adapter over a communication network.
 9. Thesystem of claim 8, wherein the graphics adapter is configured totransmit said plurality of packets to said destination device over saidcommunication network.
 10. The system of claim 8, wherein the graphicsadapter is configured to compress said selected blocks of graphics imagedata prior to formatting said selected blocks of graphics image data.11. The system of claim 8, wherein the graphics adapter is configured toadd identification information identifying said selected blocks to saidplurality of packets.
 12. The system of claim 11, wherein saididentification information comprises coordinate information for aplurality of corners of said selected blocks.
 13. The system of claim 8,wherein the graphics adapter is configured to compare the graphics imagedata in response to receiving a request for graphics image data fromsaid destination device.